1. Field of the Invention
The present invention relates to an image processing apparatus, a method of displaying an image, an image display program, and a recording medium having the image display program recorded thereon, and more particularly, to a calibration process in an optical touch panel, for example, using a twin-lens camera-attached reproduction apparatus.
2. Description of the Related Art
Many techniques are proposed for realizing a so-called touch UI (User Interface) by calculating the position (touch position) pointed by a finger, a pen, or the like on a screen using a plurality of cameras or the like. Such a touch UI is known as an optical touch panel and is applied to an electronic blackboard, a display device connected to a personal computer, and the like.
FIG. 1 is a diagram illustrating an example of an optical touch panel that realizes a touch UI. Generally, an optical touch panel is configured by an external output device 1 and two cameras 2 and 3 that are mounted on the left and right sides of the upper portion thereof. When a distance L between lenses of the two cameras 2 and 3 and angles α and β from each camera to a touch position are known, distances L1 and L2 between the cameras 2 and 3 and the touch position on the screen are acquired, thereby the touch position can be calculated. In addition, the external output device 1 may have a display function. Examples of the external output device 1 include a television set, a display device, and the like.
Actually, it is difficult to precisely measure the distance between a camera and a touch position on the screen by using only the cameras. Thus, as illustrated in FIG. 1, infrared-ray transmitting function is implemented in the cameras 2 and 3, and a frame la that is used for reflecting the infrared rays is arranged on both side portions and the lower portion of the external output device 1. There are many optical touch panels that employ a form in which infrared rays are emitted from the cameras 2 and 3, and the position of a portion is calculated for which the emitted infrared rays are blocked by a finger 4 or the like and are not returned from the frame 1a. In a case where the precision is demanded in units of the tip end of a pointer of an electronic blackboard or the like or a finger, the precision of position detection is increased by using infrared rays or the like. However, in a case where an object such as a hand or the like having a relatively large size may be approximately perceived, only cameras may be used even in the current technology.
In optical touch panels that are applied to a general electronic blackboard, a display device connected to a personal computer, or the like, cameras are fixed to the external output device. Thus, such optical touch panels are shipped after being adjusted in a factory or the like such that an actual touch position on the screen and a detected touch position coincide with each other. However, in a case where position checking sensors such as cameras are removable, error in the detected position of the touch position occurs in the optical touch panels due to mounting positions when the sensors are not correctly mounted in the external output device. Accordingly, in order to perform analysis of the relative position between the sensor and the screen, a calibration process is necessary.
FIGS. 2A to 2C are diagrams illustrating cases where error in the detected position occurs in an optical touch panel using a twin-lens camera. As illustrated in FIG. 2A, in a case where the twin-lens camera 12 is mounted at the center of the upper portion of the frame 11 arranged on the periphery of the screen of the external output device 10, a touch position A is detected based on angles α and β formed from each lens of the twin-lens camera 12 toward the touch position A. On the other hand, as illustrated in FIG. 2B, in a case where the twin-lens camera 12 is mounted at a position deviated to the right side from the center of the upper portion of the frame 11 arranged on the periphery of the screen of the external output device 10, the touch position A is detected based on angles α′ and β′ formed from each lens of the twin-lens camera 12 toward the touch position A on the screen.
Accordingly, in a case where the deviation of the twin-lens camera 12 from the center of the upper portion of the frame 11 of the external output device 10 is not known, a touch position is calculated on a premise that the twin-lens camera 12 is mounted at the center thereof. In other words, as illustrated in FIG. 2C, not the touch position A but a touch position A′ is incorrectly recognized to have been pointed. In order to resolve this, a calibration operation is necessary for a camera that is removable from the external output device when the camera is mounted in the external output device.
Several calibration methods are proposed. Generally, in order to perform a calibration process, it is necessary for the positions of several points on the screen to be correctly recognized. As an example, there is a calibration method using an information input auxiliary sheet in which calibration marks are formed in two or more corner portions and the center portion (for example, see JP-A-2009-043228).
As an advanced type thereof, in order to allow a plurality of the positions of points on the screen to be correctly recognized, a calibration method is proposed in which a confirm button (icon) is displayed at a position desired to be pressed on the screen (for example, see JP-A-2004-054413).
FIG. 3 is a diagram illustrating a general calibration method. As points for calibration, at least three points are displayed on the corners of the screen of the external output device 10 and are sequentially touched by a user. Then, a correction value used for correcting the positional relationship between a touch position and the twin-lens camera 12 (sensor) is calculated and is added to a value acquired through triangulation, thereby the error in the detected position is corrected. Furthermore, by increasing the number of points, error can be corrected with higher precision.